Revenue Recognition - Disaggregation of Operating Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Operating revenues	$ 549,842	$ 517,099	$ 498,180	$ 478,423	$ 443,661	$ 425,333	$ 409,616	$ 416,780	$ 2,043,544	$ 1,695,390	$ 1,557,796
Index [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									1,251,764	1,016,495	920,937
Analytics [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									544,299	513,808	496,925
ESG and Climate [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									166,192	111,364	90,659
All Other - Private Assets [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									81,289	53,723	49,275
Recurring Subscriptions [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									1,426,040	1,248,175	1,154,040
Recurring Subscriptions [Member] | Index [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									650,629	580,393	530,968
Recurring Subscriptions [Member] | Analytics [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									533,178	506,301	486,282
Recurring Subscriptions [Member] | ESG and Climate [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									162,609	109,945	89,563
Recurring Subscriptions [Member] | All Other - Private Assets [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									79,624	51,536	47,227
Asset-based Fees [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									553,991	399,771	361,927
Asset-based Fees [Member] | Index [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									553,991	399,771	361,927
Non-recurring [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									63,513	47,444	41,829
Non-recurring [Member] | Index [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									47,144	36,331	28,042
Non-recurring [Member] | Analytics [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									11,121	7,507	10,643
Non-recurring [Member] | ESG and Climate [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									3,583	1,419	1,096
Non-recurring [Member] | All Other - Private Assets [Member]
Disaggregation Of Revenue [Line Items]
Operating revenues									$ 1,665	$ 2,187	$ 2,048